The present invention relates to a process for producing hydrocarbonaceous products from synthesis gas.
Various processes for converting synthesis gas into hydrocarbonaceous products are well known. For example, Fischer-Tropsch synthesis is a well known method for the conversion of remote natural gas into salable products such as liquefied petroleum gas (LPG), condensate, naphtha, jet fuel, diesel fuel, other distillate fuels, lube base stock, and lube base stock feedstock. The Fischer-Tropsch synthesis process produces products that are predominantly linear hydrocarbons. These linear hydrocarbons are desirable for use in distillate fuels and as a lube base stock feedstock because they do not contain cyclic hydrocarbons. The linear structure of the hydrocarbons give them excellent burning properties when used as fuels and a high viscosity index when used as a lube base stock. The non-paraffinic linear hydrocarbons produced from the Fischer-Tropsch synthesis (e.g., olefins and alcohols) can be converted into linear paraffins by hydrogenation (e.g., hydrotreating, hydrofinishing, and/or hydrocracking).
The products from the Fischer-Tropsch process are not ideal, however, for use as a gasoline blend stock or in petrochemical operations. These uses require the presence of either aromatics or highly branched iso-paraffins, the production of which requires the use of naphtha reforming and/or alkylation processes. The low molecular weight products of the Fischer-Tropsch process that are rich in linear olefins could be converted to high octane alkylate if a source of iso-butane were available. Although iso-butane could be made from a conventional Fischer-Tropsch process by saturation of a butane stream followed by isomerization, the process would be expensive.
Another process for converting synthesis gas into hydrocarbonaceous products is the dual functional syngas conversion process. This process was developed from Isosynthesis, a process developed in Germany in the 1930""s with the objective of making low molecular weight iso-paraffins using Thoria catalysts at high pressures. More recently, Isosynthesis has evolved to use at least two different types of catalysts that both make methanol and consume it. Iso-paraffins are again a major component of the product, and this dual functional syngas conversion process can also be referred to as modern Isosynthesis. The products from the modern dual functional syngas conversion reactor are a mixture of low molecular weight iso-paraffins and an aromatic-rich product.
However, the dual functional syngas conversion process does not make products that can readily be converted into jet fuel, diesel fuel, other distillate fuels, lube base stock, or lube base stock feedstock. Light gases produced by the dual functional syngas conversion process are rich in iso-butane, but it is not easy to convert this product into fuels because to do so would require the process steps of dehydrogenation, oligomerization, and alkylation.
Accordingly, there is a need in the art for an economic and efficient process for converting synthesis gas into a full range of hydrocarbonaceous products.
The present invention relates to processes for converting synthesis gas into hydrocarbonaceous products. In one aspect of the present invention, a process for converting synthesis gas into hydrocarbonaceous products is provided comprising the steps of (a) subjecting a first portion of synthesis gas to a dual functional syngas conversion process to form a first effluent comprising a first hydrocarbonaceous product including aromatics and iso-paraffins; (b) subjecting a second portion of synthesis gas to a Fischer-Tropsch synthesis process to form a second effluent comprising a second hydrocarbonaceous product including linear paraffins and linear olefins; and (c) alkylating the linear olefins with the iso-paraffins to produce high octane gasoline range alkylate.
In another aspect of the invention, a process for converting synthesis gas into hydrocarbonaceous products is provided comprising the steps of (a) providing a synthesis gas; (b) subjecting at least a portion of the synthesis gas to a dual functional syngas conversion process to form a first effluent comprising unreacted synthesis gas and a first hydrocarbonaceous product including aromatics and iso-paraffins; (c) subjecting the unreacted synthesis gas to a Fischer-Tropsch synthesis process to form a second effluent comprising a second hydrocarbonaceous product including linear paraffins and linear olefins; and (d) alkylating the linear olefins with at least a portion of the iso-paraffins to produce high octane gasoline range alkylate.
In a further aspect of the present invention, a process for converting synthesis gas into hydrocarbonaceous products is provided that comprises the steps of (a) providing a synthesis gas; (b) subjecting at least a portion of the synthesis gas to a dual functional syngas conversion process to form a first effluent comprising a first portion of unreacted synthesis gas, carbon dioxide, a first portion of water, and a first hydrocarbonaceous product including aromatics and iso-butane; (c) separating the first hydrocarbonaceous product into a light gas fraction, an iso-butane-containing stream, and a high octane aromatic gasoline blend component; (d) subjecting the unreacted synthesis gas to a Fischer-Tropsch synthesis process to form a second effluent comprising a second portion of water, a second portion of unreacted synthesis gas, and a second hydrocarbonaceous product including linear paraffins and linear olefins; (e) separating the second hydrocarbonaceous product into a light gas stream, a C3-C4 olefin-containing stream, a C3-C4 alcohol-containing stream, and a C5+ stream; (f) combining the C3-C4 olefin-containing stream and the C3-C4 alcohol-containing stream to form a combined stream; (g) reducing the oxygen content of the combined stream to below 4000 ppm by dehydration; and (h) alkylating the combined stream with the iso-butane-containing stream to produce high octane iso-paraffinic gasoline range alkylate.
Unless otherwise stated, the following terms used in the specification and claims have the means given below:
xe2x80x9cAromaticxe2x80x9d means a molecular species that contains at least one aromatic function.
xe2x80x9cJet fuelxe2x80x9d means a material suitable for use in turbine engines for aircraft or other uses meeting the current version of at least one of the following specifications:
ASTM D1655-99
DEF STAN 91-91/3 (DERD 2494), TURBINE FUEL, AVIATION, KEROSINE TYPE, JET A-1, NATO CODE: F-35
International Air Transportation Association (IATA) xe2x80x9cGuidance Material for Aviation Turbine Fuels Specificationsxe2x80x9d, 4th edition, March 2000
United States Military Jet fuel specifications MIL-DTL-5624 (for JP-4 and JP-5) and MIL-DTL-83133 (for JP-8)
xe2x80x9cDiesel fuelxe2x80x9d means a material suitable for use in diesel engines and conforming to the current version at least one of the following specifications:
ASTM D 975xe2x80x94xe2x80x9cStandard Specification for Diesel Fuel Oilsxe2x80x9d
European Grade CEN 90
Japanese Fuel Standards JIS K 2204
The United States National Conference on Weights and Measures (NCWM) 1997 guidelines for premium diesel fuel
The United States Engine Manufacturers Association recommended guideline for premium diesel fuel (FQP-1A)
xe2x80x9cGasolinexe2x80x9d means a material suitable for use in spark-ignition internal-combustion engines for automobiles and light trucks (motor gasoline) and in piston engine aircraft (aviation gasoline) meeting the current version of at least one of the following specifications:
ASTM D4814 for motor gasoline
European Standard EN 228 for motor gasoline
Japanese Standard JIS K2202 for motor gasoline
ASTM D910 for aviation gasoline
ASTM D6227 xe2x80x9cStandard Specification for Grade 82 Unleaded Aviation Gasolinexe2x80x9d.
UK Ministry of Defense Standard 91-90/Issue 1 (DERD 2485), GASOLINE, AVIATION: GRADES 80/87, 100/130 and 100/130 LOW LEAD
xe2x80x9cDistillate fuelxe2x80x9d means a material containing hydrocarbons with boiling points between approximately 60xc2x0 F. to 1100xc2x0 F. The term xe2x80x9cdistillatexe2x80x9d means that typical fuels of this type can be generated from vapor overhead streams from distilling petroleum crude. In contrast, residual fuels cannot be generated from vapor overhead streams by distilling petroleum crude, and are then non-vaporizable remaining portion. Within the broad category of distillate fuels are specific fuels that include: naphtha, jet fuel, diesel fuel, kerosene, aviation gas, fuel oil, and blends thereof.
xe2x80x9cLube base stockxe2x80x9d means a material having a viscosity greater than or equal to 3 cSt at 40xc2x0 C., a pour point below 20xc2x0 C. preferably at or below 0xc2x0 C., and a VI greater than 70, preferably greater than 90. It is optionally used with additives, and/or other base stocks, to make a finished lubricant. The finished lubricants can be used in passenger car motor oils, industrial oils, and other applications. When used for passenger car motor oils, base stocks meet the definitions of the current version of API Base Oil Interchange Guidelines 1509.
xe2x80x9cNaphthaxe2x80x9d means a light hydrocarbon fraction composed of C5-C9 hydrocarbonaceous compounds used in the production of gasoline, solvents, and as a feedstock for ethylene.
xe2x80x9cIso-paraffinxe2x80x9d means a non-cyclic and non-linear paraffin with the formula CnH2n+2.
xe2x80x9cSynthesis gasxe2x80x9d or xe2x80x9csyngasxe2x80x9d means a gaseous mixture of hydrogen and carbon monoxide, and may also contain one or more of water, carbon dioxide, unconverted light hydrocarbon feedstock, and various impurities such as sulfur or sulfur compounds and nitrogen. The synthesis gas or gases used in the present invention may be derived from a variety of sources such as, for example, methane, light hydrocarbons, coal, petroleum products, or combinations thereof. Such sources can be used to generate synthesis gas through processes such as, for example, steam reforming, partial oxidation, gasification purification of synthesis gas, and combinations of these processes. More specific examples of processes for generating synthesis gas include the reforming of methane or the gasification of coal or petroleum products such as resid.
xe2x80x9cHydrocarbonaceousxe2x80x9d means containing hydrogen and carbon atoms and potentially also containing heteroatoms such as oxygen, sulfur, or nitrogen.
xe2x80x9cFull range of hydrocarbonaceous productsxe2x80x9d means a range of hydrocarbonaceous products including, but not limited to, high octane blend streams, jet fuel, diesel fuel, other distillate fuels, lube base stock, and lube base stock feedstock.
xe2x80x9cHigh octane gasoline range alkylatexe2x80x9d is a product of an alkylation process having high octane.
xe2x80x9cHigh octane aromatic gasolinexe2x80x9d means a Gasoline with a high octane containing greater than 25 wt % aromatics preferably greater than 50 wt % aromatics. xe2x80x9cHigh octane gasoline blendxe2x80x9d or xe2x80x9chigh octane gasoline blend componentxe2x80x9d means is a material that has greater than 85 octane by the research octane method, preferably greater than or equal to 90, most preferably greater than or equal to 95. Research Octane Numbers are measured by ASTM D2699 xe2x80x9cStandard Test Method for Research Octane Number of Spark-Ignition Engine Fuelsxe2x80x9d